After I sunk my boat a few times the 7 cells I put into my boat right after I took them off the charger, it ran like crap so i think they need to cool down for at least a half hour till cooled. Also a blow dryer after it sinks. Today I let the batteries cool off the charger for about 45 min and the boat just screamed ran perfect but then I tried running it after taking the batteries right off of charge and it sucked again. So maybe let the batteries cool. The batteries put in right after the charge made the boat flip and sink.
I had 3 perfect runs with the 7 cells after I let them cool before putting them in.